1. Field of the Invention
This invention relates to a controlled deflection roll of the type which is commonly used in the press and calender sections of a papermaking machine. More particularly, this invention relates to a self-loading type of controlled deflection roll wherein the roll shell can translate relative to the longitudinal axis of the roll. Still more particularly, this invention relates to a self-loading, controlled deflection roll wherein the roll shell is stabilized by pivotally mounted, adjustably positionable side guide shoe apparatus.
2. Description of the Prior Art
The art relating to self-loading types of controlled deflection rolls having means for stabilizing the roll shell relative to the stationary center shaft during operation is rapidly evolving. An example of such a stabilized self-loading, controlled deflection roll is the subject of pending U.S. patent application Ser. No. 07/541,678 filed Jun. 21, 1990 and commonly assigned with this invention. The subject matter of the application Ser. No. 07/541,678 is hereby incorporated by reference. In that application, a pair of opposed guide shoes are disposed on either side of the center shaft in a self-loading, controlled deflection roll. They are mounted to slide on substantially parallel surfaces in the direction of the plane of the nip with a mating roll. At least one of the shoes includes a piston within an interface between a piston member and an associated guide shoe for permitting radial movement of the opposed guide shoes relative to the stationary support shaft in a plane substantially perpendicular to the plane of the nip with a mating roll.
The problems associated with stabilizing the roll shell in a self-loading type of controlled deflection roll have not long been recognized because self-loading, controlled deflection rolls operating in the field are relatively new. In one type of self-loading, controlled deflection roll, which is described and illustrated in Biondetti U.S. Pat. No. 3,885,283, a pair of collars, each having a pair of flat, parallel surfaces, are disposed at either end of the roll shell to slide over corresponding surfaces on the stationary roll shaft to allow the roll shell to translate reciprocally in its nip plane while the roll shell is rotatably supported about the outer, cylindrical surfaces, which might include bearings, on each of the collars. Lateral stabilization of the roll shell is a function of the clearance between the collars and parallel surfaces on the shaft. The clearance does not provide support.
In Arav, U.S. Pat. No. 4,821,384, diametrically opposed nip loading shoes are positioned in the stationary shaft of a controlled deflection roll to move the roll shell radially inwardly and outwardly in opposed directions relative to the shaft to load and unload the nip. A pair of laterally disposed guide shoes are positioned at either end of the roll to stabilize the roll shell. However, the opposed guide shoes are of a unitary design which limits the extent of the translational movement of the roll shell relative to the stationary support shaft due to the inability of the guide shoes to extend and contract as the radial distance of the inner periphery of the roll shell changes relative to the support surfaces of the guide shoes on the roll shaft during translational movement of the roll shell. The Arav guide shoes cannot compensate for thermal expansion or for dimensional differences caused by manufacturing tolerances. Also, the gap along the interface between the guide shoes and their support surfaces on the roll shaft can only extend for a limited distance radially before the required hydraulic pressure required to maintain the roll shell in a desired position decreases as a function of the increased gap.
Thus, in prior self-loading types of controlled deflection rolls having means for stabilizing the rotating roll shell, deficiencies or inefficiencies in either their structure or mode of operation limit their effectiveness or competitive advantage. In other words, the roll shell stabilization either limits the extent, or travel, of the self-loading capability of the roll, or the apparatus is structurally complicated and expensive.